Reviewed by Mustafa Bilgic
Founder, WebCalculator · Last updated 26 July 2026
Penalty rates are from HMRC's self assessment penalties page. Estimates only — not financial or legal advice.
Missed the self assessment deadline? This calculator shows exactly how much HMRC will charge you in late filing penalties and late payment surcharges, based on how many days overdue your return or payment is. The 2025/26 return is due by 31 January 2027 — a return filed even one day late triggers a £100 fixed penalty.
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HMRC imposes two separate sets of penalties: one for filing your tax return late, and one for paying your tax late. Both can apply at the same time.
| How late | Penalty |
|---|---|
| 1 day late | £100 fixed (even if no tax owed) |
| 3 months late | £10 per day for up to 90 days (max £900) |
| 6 months late | 5% of tax due or £300 (whichever is greater) |
| 12 months late | 5% of tax due or £300 (whichever is greater) |
The maximum filing penalty for a return that is over 12 months late with £2,000 of tax due is £100 + £900 + £300 + £300 = £1,600. If more tax is due, the 5% charges at 6 and 12 months can be significantly higher.
| How late | Penalty |
|---|---|
| 30 days late | 5% of tax unpaid at that date |
| 6 months late | Additional 5% of tax still unpaid |
| 12 months late | Additional 5% of tax still unpaid |
On top of the surcharges, HMRC charges daily interest on all unpaid tax at the Bank of England base rate plus 2.5 percentage points. The interest is not included in this calculator because it depends on the exact dates and rate changes.
If you need time to pay, contact HMRC before the deadline to set up a Time to Pay arrangement — this can prevent late payment penalties, though interest still applies.
For help calculating the tax you owe, use the self-employed tax calculator or the income tax calculator.
If your return is up to 3 months late you receive a £100 fixed penalty — even if you owe no tax. After 3 months HMRC adds £10 per day for up to 90 days (max £900 extra). At 6 months late a further penalty of 5% of tax due or £300 (whichever is greater) is added, and again at 12 months.
If your tax is unpaid 30 days after the due date, HMRC charges 5% of the amount outstanding. A further 5% is added at 6 months, and another 5% at 12 months. Interest also accrues daily on all unpaid tax at the Bank of England base rate plus 2.5%.
The online filing deadline for the 2025/26 tax year is 31 January 2027. Paper returns have an earlier deadline of 31 October 2026. Any tax owed must also be paid by 31 January 2027.
Yes. You can appeal within 30 days if you have a reasonable excuse — for example, a serious illness, bereavement, or HMRC system failure. You appeal online through your personal tax account or by post using form SA370.
Yes. The £100 fixed penalty for a late return applies even if you owe nothing or are due a refund. The daily and percentage penalties above 3 months are based on the tax due, so they would be zero if no tax is owed.
Yes. Interest accrues daily from the due date at the Bank of England base rate plus 2.5 percentage points. This is in addition to the 5% surcharges at 30 days, 6 months and 12 months.